New Technique for measuring electron density under soiled conditions and its application for precise process control

在亚微米结构的下一代ULSI器件的制造中，为了提高制造精度，应该开发用于各种加工（如蚀刻）的极其稳定和可控的等离子体源。为了实现这一目标，通过监测等离子体状态对等离子体进行反馈控制是可取的。在本研究中，我们开发了一种传统但功能强大的电子密度监测工具“等离子体吸收探针”，即使在污染条件下的过程等离子体中也可以使用。在探针中，表面波在探针尖端被激发，提供给探针尖端的部分射频功率通过表面波在几个频率上共振吸收到等离子体中。吸收频率直接给出表面波的共振频率，进而给出电子密度。考虑到探针周围形成的护套，该探针使我们能够测量实际氟碳蚀刻等离子体中从10^<14> m^<-3>到超过10^<18> m^<-3>的宽电子密度范围内的电子密度。

In a fabrication of sub micron struction for next-generation ULSI devices, extremely stable and controlled plasma sources for various processing such as etching should be developed in order to improve fabrication accuracy. To achieve that, feed-back control of the plasma by monitoring the plasma condition is preferable. In the present reseach, as a conventional but powerful tool for electron density monitoring, we have, developed the "Plasma Absorption Probe" usable even in the process plasma of soiled conditions.In the probe, surface waves are excited at the probe tip, and a part of RF powers supplied to the probe tip is resonantly absorbed to the plasma through the surface waves at several frequencies. The absorption frequencies directly gives resonant frequency of the surface wave, in turn electron density. Considering the sheath formed around the probe, the probe enables us to measure the electron density in the wide electron density range from 10^<14> m^<-3> to over 10^<18> m^<-3> in actual fluorocarbon etching plasmas.